<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    * {
        padding: 0;
        margin: 0;
    }
    header {
        height: 100px;
        background-color: pink;
    }
    main {
        height: 500px;
        background-color: purple;
    }
    .w {
        width: 1200px;
        margin: auto;
    }
</style>
<body>
    <header></header>    
    <div class="w">
         <main></main>
    </div>
    
</body>
</html>